In the realm of power-limited electronic devices such as smartphones, laptop computers, tablet computers, and portable music playing and gaming devices, there are a number of electronic subsystems in each device that can operate relatively independently in that each subsystem can be called upon to perform a task at any given moment and each subsystem has its own thermal and power performance behavior. Examples of such subsystems are a system-on-a-chip (SoC) circuit, a central processing unit (CPU), a graphics processing unit (GPU), a cellular phone network communications interface, a digital camera, a touchscreen, a display backlight system, a radio frequency (RF) transceiver system, a battery charging system, and various sensors such as a proximity sensor and an inertial sensor. For example, a cellular phone call will cause the cellular RF transceiver and a baseband communications processor to consume significantly more power which in turn causes a rapid increase in temperature at their locations inside a smartphone, while the temperature in other subsystems might rise much more slowly. When the detected power and/or thermal performance of a power-limited electronic device exceeds a certain pre-determined level, a power and/or thermal management system in the device may “throttle” the power consumption of one or more of the subsystems so as prevent excessive temperatures or excessive battery discharge.